Anti-shrinkage agent for hydraulic material

Abstract

The present invention is related to a shrinkage reducing agent for hydraulic materials which comprises at least one polymer selected from the group consisting of (a) a polymer having a structure derived from the residue of a compound containing 2 to 30 carbon atoms and one active hydrogen atom by the binding thereto of one oxyalkylene chain having a carboxyl-containing side chain, (b) a polymer having a structure derived from the residue of a compound containing 4 to 30 carbon atoms and two active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain, (c) a polymer having a structure derived from the residue of a compound containing 1 to 30 carbon atoms and at least three active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain and (d) a polymer having a structure derived from the residue of an amine by the binding thereto one oxyalkylene chain having a carboxyl-containing side chain.

Description

[0001] The present invention relates to a shrinkage reducing agent for hydraulic materials, a method of producing the same and an additive composition for hydraulic materials.PRIOR ART[0002] Hydraulic materials can give cured products excellent in strength and durability, among others, and therefore are in wide use in the form of cement compositions such as cement pastes, mortar and concrete. They are now indispensable in building civil engineering and architectural structures. Such hydraulic materials, however, have a problem. After curing, the unreacted water remaining in the inside disperses according to ambient temperature, moisture and other conditions and drying shrinkage progresses presumably due to such moisture dissipation to cause cracks to appear in cured products, lowering the strength and durability thereof. Decreases in strength and durability of civil engineering and architectural structures produce serious problems such as endangered safety and increased repairing co...

AI Technical Summary

Benefits of technology

[0088] The above-mentioned shrinkage reducing agent for hydraulic materials according to the invention may be made into an additive composition for hydraulic materials by incorporating therein such ingredients as mentioned later herein. The composition can produce various effects on hydraulic materials while producing the effects of the invention. The concentration of the shrinkage reducing agent for hydraulic materials in the additive composition for hydraulic materials is not particularly restricted.

Problems solved by technology

Such hydraulic materials, however, have a problem.

After curing, the unreacted water remaining in the inside disperses according to ambient temperature, moisture and other conditions and drying shrinkage progresses presumably due to such moisture dissipation to cause cracks to appear in cured products, lowering the strength and durability thereof.

Decreases in strength and durability of civil engineering and architectural structures produce serious problems such as endangered safety and increased repairing costs.

However, the standard addition amounts of these shrinkage reducing agents are as high as 2 to 6% on the unit cement content basis, so that when used in concrete, they increase the cost of concrete and can never be said to be general purpose agents.

However, this is not easy to synthesize.

However, when the hydrophobicity is excessive, the amount of air in concrete may be reduced to an excessive extent, hence the adjustment of the amount of air may become difficult.

When the hydrophilicity is excessive, an excessive amount of air may be entrained, so that it may possibly become difficult as well to adjust the amount of air to an appropriate level.

When the hydrophobicity of the polymer is excessive, the amount of air in concrete is excessively reduced and accordingly it becomes difficult to control the amount of air.

Conversely, when the hydrophilicity of the polymer is excessive, an excessive amount of air is entrained in the hydraulic material and it becomes difficult to adjust the amount of air to an appropriate level.

When the amount of the ethylenically unsaturated carboxylic acid monomer is less than 0.1% by weight, the resulting polymer will hardly act on cement, possibly resulting in a decrease in shrinkage reducing ability.

When it is in excess of 100 parts by weight, the retardation of curing by the polymer may be enhanced or the reaction mixture will acquire an excessively high viscosity and thus become difficult to handle.

The addition amount of the shrinkage reducing agent for hydraulic materials is larger than the above weight ratio, the water reducing ability of the air entraining and high-range water reducing agent may be impaired.

When it exceeds 10% by weight, hydraulic materials may possibly undergo curing retardation.

When the amount is less than 0.0001% by weight, the shrinkage reducing ability is not sufficiently effected.

When it exceeds 10% by weight, hydraulic materials may possibly undergo curing retardation.

When the amount of water is less than 10% by weight, the respective ingredients are mixed only to an insufficient extent, so that the compositions cannot be molded in some instances or the strength may decrease in other cases.

When it is larger than 80% by weight, the strength of cured products obtained from the cement compositions may possibly decrease.

When it exceeds 60% by weight, higher unit cement content and unit water content are required, possibly giving concrete poor in flowability.

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